This proposal is concerned with the genetic dissection of the process of meiotic recombination in Drosophila melanogaster females by means of mutants which alter the frequency and/or distribution of exchange events (recombination-defective mutants). Two aspects of meiotic recombintion can be monitored: intergenic (reciprocal) recombination and intragenic (reciprocal or nonreciprocal; gene conversion). Both aspects display a number of regularities in wild-type flies; the recombination-defective mutants will be used to probe the genetic control of these attributes, their interrelationships, and, most importantly, the relationship between intergenic and intragenic events. Preliminary data indicate that a recombination-defective mutant at one locus (mei-9) that reduces intergenic exchange by more than an order of magnitude does not cause a decrease in the frequency of intragenic exchange. Moreover, the products of intragenic exchanges recovered from mei-9 exhibit frequent postmeiotic segregation, a phenomenon almost never observed in non-mutant controls.